I'll probably do this one over again now that I have a better sense of what's involved. 1) The moss is way too long and bushy, and 2) I exposed too much soil along the glass sides (not pictured).
I used three kinds of moss -- Scottish, Irish, and something packaged as "Frog Moss" I found at a pet store. The mini "trees" are Myoporum, typically used as a groundcover. Not sure how they'll do w/ the moss as their sun and water needs are different. They're supposed to flower in spring and summer (with the right conditions).
The small terrarium in the last pic is from madebymavis at Etsy, a gift from Lisa.